This invention relates generally to the field of cylindrical can decorating or printing equipment, and more particularly relates to inker assemblies utilized in such can decorating equipment.
Decorating equipment that apply ink to cans or similarly shaped articles using offset printing techniques are known. Ink of a particular color is transferred from an ink fountain assembly to a plate cylinder and printing blanket by an inker assembly comprising a number of rotating rolls or drums, the ink. Certain rolls known as transfer rolls are typically ceramic coated, while other rolls known as doctor rolls, distributor rolls and form rolls are coated with a closed cell polymer. In known designs the transfer rolls are axially oscillated relative to the other rolls to preclude “ghosting”, the unwanted retention and transfer of a printing plate image on the rollers where the ink has been removed and not reapplied or smoothed by the oscillating rolls. This creates problems in that the oscillating transfer rolls are composed of steel, are water cooled and gear driven, which requires significant energy to operate and will produce vibration in the system from the inertia resulting from the rapid axial movement. Significant heat is generated in the transfer rolls, which results in frequent shaft seal failure and leaking oil. Gear driven systems also require water cooling of the oil in the gearbox, which often results in oil leaks near the printing plates and blankets. The gear driven systems do not provide for independent adjustment of the oscillating frequency during operation. Furthermore, current designs are not easily disassembled, such that removal of the inker assembly for cleaning or replacement is time and labor intensive. Current designs have other problems in addition to those listed above, and it is an object of this invention to address a number of problems inherent in the current designs.